With the increasing demand, from a performance standpoint, on portable computers, such as notebook computers, laptop computers, personal digital assistants, and the like, it is becoming increasingly difficult to keep the temperature of the computer below an acceptable value. This problem is compounded by an increased demand for power which requires additional batteries that generate additional heat and take up extra space.
Passive cooling of a portable computer is preferred due to increased battery time, reliability and reduced noise. Since much of a portable computer's passive cooling is accomplished through the keyboard and palmrest areas, the heating problem becomes even more acute when the computer is docked in a docking station since, when docked, the display is generally closed, essentially blocking the cooling path through the keyboard and palmrests.
The docking stations themselves also contribute to the cooling problem since they are usually fabricated from a plastic material and use a tray to provide gross alignment between a connector on the docking station and a mating connector on the computer. Due to assembly tolerances, most docking connectors are located slightly higher than the computer connector, causing the computer to be lifted above the tray when connected. Also, since it is generally objectionable to slide a large portion of the computer over the docking surface at the risk of wear to the plastic surface, docking stations often use rails to minimize the sliding contact or rely on the notebook feet as the slide surface. In both of these designs, an air gap is created between the notebook and the docking station which acts as an insulator and thus minimizes the transfer of heat from the computer. Also, since plastic is a poor heat conductor, the possibility of removing any heat from the bottom surface of the notebook by heat conduction is further reduced.
At least one form of dock-assisted cooling has been proposed to lower the temperature of the docked portable computer to an acceptable value. In these designs, a rear-mounted cooling fan is provided on the computer to draw air into the computer and exhaust it to the rear, and the docking station has a matching duct with a fan in order to serially pull more air through the computer. Although this does, in fact, lower the temperature of the docked computer, it is a less than optimum solution for several reasons. For example, fans traditionally have a relatively high failure rate and are noisy. Also, the notebook "exhaust" point takes up valuable real estate in the interior of the computer, and minimizes design flexibility.
Therefore what is needed is a portable computer and a docking station for the computer in which the temperature of the computer is reduced during docking without the disadvantages discussed above.